N-doped Ti3+ rich SrTiO3 for efficient photoelectrochemical water splitting

In this work, hydrothermally synthesized SrTiO3 (STO) is subjected to ammonia reduction for 15 h and 45 h at 1000 ℃ under controlled conditions. The ammonia treatment reduced the band gap of SrTiO3 from 3.2 eV to 2.8 eV in ammonia-treated SrTiO3 samples (STON). XRD and Raman analysis confirm the presence of cubic phase in the STO and ammonia-treated STON-15 and STON-45 samples. Additionally, the presence of N due to ammonia reduction in STON-15 and STON-45 samples is verified by XPS analysis. In addition, XPS data shows an increase in the Ti3+ concentration in the STON-15 sample relative to the STON-45 sample when N is incorporated. STON-15 showed higher photocurrent density throughout the potential range of water splitting. An increase from 98 μA/cm2 to 250 μA/cm2 in the cathodic photocurrent density at 0 VRHE is obtained for STON-15 sample compared to STO sample. In contrast to STO, which only displayed a photocurrent density of 4.97 μA/cm2, STON-15 showed an anodic photocurrent density of 140 μA/cm2 at 1.23 VRHE. All the photoelectrochemical studies were carried out without using co-catalysts and sacrificial agents. [Display omitted] •Nitrogen incorporated into SrTiO3 lattice in ammonia flow•Band gap of nitridated samples reduced to 2.8 eV.•Shallow trap states created successfully to trap the photoexcited electrons.•STON-15 shows overall photocurrent density of 250 μA/cm2 @ 0 VRHE.•STON-15 is photostable for 4000 s @ 0.3 VRHE.